Medical electrical stimulation is currently used for a variety of reasons. Among the fastest growing indications for medical electrical stimulation is the treatment or suppression of pain.
Medical electrical stimulation typically treats pain through the application of electrical pulses to a nerve or nerve fibers. Generally speaking, one of the difficulties with providing electrical stimulation to nerve fibers is to provide an adequate, simple and reliable coupling of the treatment electrodes with the nerve fibers.
One nerve which may be in need of electrical stimulation to treat pain is the trigeminal nerve. The trigeminal nerve is the largest of the facial nerves.
Trigeminal neuralgia is a malfunction of this nerve which causes (usually) spasmodic pain. Any of the three branches can be affected. The pain can be caused by one or more of several causes.
Pressure of a blood vessel on the root of the nerve. PA1 Demyelinization of the nerve (i.e. the destruction of the myelin sheath that protects the nerve fiber). PA1 Physical damage, such as failed dental procedures or infections. PA1 Unknown. Not all cases seem to have a clear cause.
Only one side of the face is usually affected, but trigeminal neuralgia of both sides is also known to exist. In "classical" trigeminal neuralgia, the pain is extremely sharp and seizure-like. It is often triggered by certain stimuli such as touching the face, eating, talking, shaving, etc. These triggers vary from person to person.
When a blood vessel is suspected to be pressing on the root entry zone, an operation, aimed at removing the source of the compression, requires a craniotomy at the base of the skull. This bony opening is often very small, referred to as "key hole" surgery.
Symptom relief is usually obtained through microvascular compression where offending blood vessel is physically moved away from the root entry zone. On occasion, a more radical approach is required such as partial or complete cutting of the nerve. This procedure is very effective and long lasting, particularly if an artery is found compressing the nerve as it enters the brainstem.
Common complications from rhizotomy procedures include facial or eye numbness, change in bite and TMJ problems. Serious complications such as strole, paralysis, blindness or death are rare. The typical complications of microsurgical vascular decompression are facial or eye numbness, deafness, coordination problems, change in bite, TMJ problems and wound healing problems.
One of the typical features of trigeminal neuralgia is that it is rarely typical. In addition to the stabbing neuralgic pain, many victims experience various kinds of pain that may be described as burning, crushing, pulsating, etc. These "typical" forms of pain are often very difficult to treat.
Trigeminal neuralgia is a very rare condition. Statistics vary, but the relevance is probably about 150 cases per million people per year. There are some relatively effective treatments for trigeminal neuralgia. Unfortunately, although some of the treatments are becoming standard, there is no single treatment that is effective for all victims.
In a so-called "key-hole" surgical operation the neurosurgeon approaches the point where the trigeminal nerve enters the brain (the root entry zone) directly, using an operating microscope, through a small opening behind the car at the affected side. The surgeon searches for, and nearly always finds, a blood vessel (usually an artery, but it could be a vein) close against the nerve, kinking the nerve. It is presumed that the physical kinking of the nerve by the offending blood vessel has a part to play in causing trigeminal neuralgia. The vessel is carefully separated from the nerve thus unkinking or decompressing the nerve. It is important to be sure that the separation of the vessel and nerve is maintained so as to reduce the chance of the condition recurring. For this purpose teflon cotton pads are placed in between the vessel and the nerve. Often, however, separation of the nerve and vessel is not sufficient and electrical stimulation is desired to suppress pain.